The Collaborative International Dictionary of English v.0.48:

Cube \Cube\ (k[=u]b), n. [F. cube, L. cubus, fr. Gr. ???? a
   cube, a cubical die.]
   1. (Geom.) A regular solid body, with six equal square sides.
      [1913 Webster]

   2. (Math.) The product obtained by taking a number or
      quantity three times as a factor; as, 4x4=16, and 16x4=64,
      the cube of 4.
      [1913 Webster]

   Cube ore (Min.), pharmacosiderite. It commonly crystallizes
      in cubes of a green color.

   Cube root. (Math.), the number or quantity which,
      multiplied into itself, and then into the product,
      produces the given cube; thus, 3 is the cube root of 27,
      for 3x3x3 = 27.

   Cube spar (Min.), anhydrite; anhydrous calcium sulphate.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cube root
    n 1: a number that when multiplied three times equals a given
         number